1. Field of the Invention
The present invention relates to a substrate processing apparatus that applies an ion beam to both surfaces of a substrate to process both substrate surfaces in manufacturing a magnetic recording disk such as a hard disk, and a magnetic recording medium manufacturing method.
2. Related Background Art
Manufacture of a magnetic recording disk such as a hard disk is roughly divided into the preceding process of performing formation of an underlayer, formation of a magnetic film for a recording layer, and formation of a protective film for protecting the recording layer, and the following process of performing, e.g., formation of a lubricant layer on the surface of the substrate on which the protective film has been formed.
In general, a magnetic recording disk has a recording layer on both surfaces of a substrate, and thus, in the aforementioned processes, various kinds of processing are performed on both surfaces of the substrate.
As a technique for processing both surfaces of a substrate as described above, for example, a technique that provides an ion gun on both sides of a substrate to emit and apply an ion beam formed from ionized argon gas from the ion gun to each surface of the substrate is disclosed (see Japanese Patent Application Laid-Open No. 2005-56535).
However, substrate processing techniques in which ion guns (ion beam generators) are arranged opposite each other on the opposite surfaces of a substrate, as in Japanese Patent Application Laid-Open No. 2005-56535, have a problem in that the opposed ion beam generators are mutually affected by their ion beams.
In particular, when using a substrate having an opening in its center like a substrate for a magnetic recording disk and applying an ion beam to both surfaces of the substrate, an ion beam from one of the ion beam generators enters the other ion beam generator through the opening of the substrate. Consequently, there are problems in that the insides of the beam generators are mutually contaminated, and/or damaged.